ozone: evdev: Use tracking id for TouchEvent finger id

ozone: evdev: Use tracking id for TouchEvent finger id

We're supposed to use a unique id that increments for each
distinct touch. That's tracking id, not slot.

BUG=none
TEST=chrome on pixel with --ash-touch-hud
NOTRY=true

Committed: https://crrev.com/f1e78836b0c4c44b5a30031761c79d13e4e9e8f7
Cr-Commit-Position: refs/heads/master@{#292306}

[spang, 2014-08-26 22:20:56]

spang@chromium.org changed reviewers:
+ alexst@chromium.org, miletus@chromium.org

[Yufeng Shen (Slow to review), 2014-08-26 23:31:55]

miletus@chromium.org changed reviewers:
+ sadrul@chromium.org

[sadrul, 2014-08-27 01:35:58]

Can you add a test in touch_event_converter_evdev_unittest.cc?

[alexst (slow to review), 2014-08-27 18:56:45]

lgtm

[spang, 2014-08-28 03:31:48]

The CQ bit was checked by spang@chromium.org

[commit-bot: I haz the power, 2014-08-28 03:33:01]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/spang@chromium.org/512553002/20001

[commit-bot: I haz the power, 2014-08-28 03:34:13]

Committed patchset #2 (id:20001) as b51e00fc35fc4172f51bd711551c7724f2428560

[commit-bot: I haz the power, 2014-09-10 02:56:59]

Patchset 2 (id:??) landed as
https://crrev.com/f1e78836b0c4c44b5a30031761c79d13e4e9e8f7
Cr-Commit-Position: refs/heads/master@{#292306}